The Secret of the Old Mill
Franklin W. Dixon
Hardcover
(Grosset & Dunlap, Aug. 16, 1970)
With two cases in tow, the Hardy boys look to Turner mill for clues. Determined to learn the secret of the old mill, Frank and Joe employ a clever ruse to gain entrance, only to find themselves trapped. How the young detectives extricate themselves from this dangerous situation and unravel mysteries will keep readers tense with suspense!